Various methods for making formed fibrous articles from fibrous materials such as cellulose or the like are well know to those of skill in the art. One common method of manufacturing such formed fibrous articles consists of defiberizing a starting material and then creating air-entrained stream of the defiberized material. The air-entrained defiberized material may be formed into a formed fibrous article through the use of a porous mold structure subjected to a vacuum to draw the defiberized material into the mold.
It is also known that formed fibrous articles of the type described above may be subjected to calendering processes to alter the mechanical and fluid handling properties of such articles. A calendering process used in the art is commonly referred to as “pin calendering”. Pin calendering employs the use of a plurality of pins adapted to compress and densify the article.
A problem associated with pin calendering processes of the type described above is that such processes typically require that a “carrier layer” be used during the pin-calendering step. “Carrier layer” as used herein means any material layer used to support the formed fibrous article, such as a conveyer belt or an adjacent material layer such a rolled nonwoven layer or the like. The use of such a carrier layer increases complexity of manufacture. In addition, if the carrier layer is a layer intended to be incorporated into the final product, the inclusion of such layer may increase the cost of the final product and/or undesirably affect the fluid handling characteristics of the product.
In view of the above the inventors of the present invention have discovered, and disclosed herein, a method and apparatus for making a pin-calendered formed fibrous article that does not require the use of a carrier layer. Formed fibrous articles according to the present invention are particularly useful as an absorbent core structure in a disposable sanitary article such as a sanitary napkin, panty liner, diaper or the like.